The Dimensional Dilemma
by Fazely
Summary: Warning: [Au! Sans x Sans! Reader] Unknown to any other Sans, there lives a secret dimensional pocket timeline called Under (). (Y/N) is the Sans of that world while their younger brother (B/N) is the Papyrus. One day, a glitchy dimensional pocket appears and poor (B/N) falls through. (Y/N) must find a way to save her brother. Along the way they meet some...unexpected allies.
1. Prologue

[A/N: Welcome to my story! I hope you like it. (Y/N)'s gender and the rest of the Undertale character's (except Papyrus) gender will be unanimous so it is up to the reader. This makes it more into their own version of Undertale.

(Y/N)'s timeline is taking place a while after the "Good Ending" of the original Undertale.]

(Y/N)'s POV

I stepped out into the snowy terrain that fell besides the doors of Toriel's place. Toriel was a pretty nice person, they were extremely kind to me and my younger brother (B/N) but everyone just calls him Papyrus. Many people asked if I had a crush on Toriel, I thought a lot about it. I actually used to when it was just me and them talking against the giant purple door. It was nice talking to them and knowing that I had another friend in this crazy world, but after meeting Toriel and getting to know them a bit more, I decided it would be best if we just stayed friends.

I sigh lightly was I walked back towards my home. Hopefully Papyrus was home, I was kinda hungry and hopefully he would make me some of his homemade (Food Choice).

It has been a year since we left the underground, many monsters were now accustomed to human life and ways. Mettaton was one example, while they were always glamorous and trendy, the became even more after moving up into the human world. They had their own human like talk show now! It's pretty popular.

At first, I didn't trust this new reality. I was sure that any minute Frisk was going to get bored and restart the world once again...but it never happened. They were happy...and slowly did I.

As I shuffle the keys to my home, I open the door to find a sleeping Papyrus and a small Frisk on their chest. How cute.

"Bro." I hummed, sitting down in the open space of the couch. He grumbled a response. I chuckled lightly and patted his shoulder softly.

After a while, I went up to my room. I slowly groaned as I laid down on my old mattress.

"Another day in the life of Sans..." I sighed quietly. My actual name is (Y/N) but people call me Sans, so I adopted the nickname. I slowly fell asleep, hoping to wake up to another day of life.

Meanwhile

"Ink!" Dream stated, walking over to his good friend.

"Huh? Yeah Dream?" He hums, looking over at the bright skeleton.

"I found another glitchy portal. What should I do?" He said, a bit panicked.

"Is that all?" The colorful skeleton chuckles.

"Just direct it to a empty dimensional pocket." He hums, waving him off. Dream sighed in relief and nodded.

Dream slowly opened up the glitchy portal.

"Now, where should I send you?" He hum to himself. He looked for a empty pocket until he found one.

"Ah! This dimension seems to be empty." He hums.

"Sorry dimension B7H92P!" He hums, apologizing to the what seemed to be the empty dimensions. He closed the glitchy portal and sent it to the dimension of his choice.

Who knew that dimension wasn't at all empty...it was something more.


	2. Chapter 1: Day in the Life of (BN)

Underfell Sans and Underfell Papyrus were walking through the cruel depths of the Underground. Suddenly they both felt a strange shiver. It wasn't a cold shiver, it was like a earthquake shiver. Something felt wrong.

"Boss, did ya feel that?" Underfell Sans said, looking at his taller brother.

"Of course I did you idiot!...What do you think it was?" His brother said, feeling uncertain.

"I dunno, ya think the other Sanses and Papyruses felt it?"

(B/N)'s POV

It was Saturday morning, my lazy sibling must be sleeping! I was so mad at (Y/N) that I didn't even want to make pancakes!

"Get up you lazy bones!" I screamed at the top of my lungs to them. All I heard was a lazy groan. I sigh as I give up and made my stupid sibling some breakfast.

I swear if I wasn't so great, I wouldn't even wake them up! That's when I heard a knock on the door. Who could it be? I was excited that it might be a new friend to make! Some people compare me to a dog, since I'm so cute, cuddly and excited all the time. It was kinda weird since I didn't like dogs, but whatever.

It was Undyne! How exciting!

"Undyne!" I yell in excitement.

"Papyrus!" They yell back.

"What are you doing here?" I hum, beautifully.

"I'm here to see Alphys but their 'busy'" Undyne said, sighing in frustration. Alphys and Undyne were dating ever since we left the Underground, it must be all of my hard work into Alphy's esteem! I'm such a good friend.

"Well, why don't we help Alphys!" I hum, always happy to help my friends. Undyne nodded in return. It was settled then! As I happily finish cooking San's food I leave a note for them.

"(Y/N), off to help Alphys in their lab! Here's some food, lazy bones!" I write and walk off with Undyne.

A while later, we go towards Alphy's new lab. It was smaller than their old one in the Underground but still functional. As we enter, Alphys seemed nervous and shaky.

"Alphys!" I said, waving towards them. They look back at me with a surprised face.

"P-Papyrus, Undyne?!" They said, looking at both of us.

"What are you two doing here?" They gulp.

"We're here to help you with whatever you're doing!" Undyne said with a brave, sharp smile. Alphys looks at us and stays quiet for a moment.

"Oh, that's really generous of you...but I wouldn't want to waste your ti-"

"Nonsense!" I say, cutting them off.

"You're not wasting our time! Our time is not wasteful!" I smile as they look at me with a sigh.

"Fine..." They say, probably knowing that Undyne and I don't take 'no' for a answer.

A few hours later,

Alphys was finished with her work, they still looked nervous though as if their problems weren't fixed. I just waved it off as Alphys kinda always looked nervous. I guess they were just a paranoid person! As the three of us watched something called "anime" together, I suddenly felt the need to go towards the bathroom.

"Excuse me guys! I need to use the restroom!" I say, walking off.

As I walk towards the bathroom, I look over the multiple lab rooms Alphys had, one in particular catches my eye. While the door was closed, I could see something glowing due to the crack under the door. What was it? I looked around, I really shouldn't peak...but...I'm just so curious! If I don't, I won't be able to sleep! I slowly open the door to see...a portal?

Woah. I walk into the room, the portal was really beautiful. Why was it here? Was this that made Alphys so nervous? I walk towards it, I couldn't stop myself...I just needed a closer look. This portal attracted me, I slowly put my hand in...then my entire body. I'm sure Alphys won't mind if I go inside.


End file.
